DEFUN-SK-EXAMPLE

For a more through, systematic beginner's introduction to quantification in
ACL2, see quantifier-tutorial.

The following example illustrates how to do proofs about functions defined
with defun-sk. The events below can be put into a certifiable book
(see books). The example is contrived and rather silly, in that it shows
how to prove that a quantified notion implies itself, where the antecedent
and conclusion are defined with different defun-sk events. But it
illustrates the formulas that are generated by defun-sk, and how to use
them. Thanks to Julien Schmaltz for presenting this example as a challenge.